Method of producing mixtures of bis (methylcyclopentadienyl) magnesium and bis (cyclopentadienyl) magnesium



United States Patent METHOD OF PRODUCING MIXTURES F BIS(METHYLCYCLOPENTADIENYL) MAGNESIUM AND BIS (CYCLOPENTADIENYL) MAGNESIUMWilliam A. Barber, Springdale, Conn., assignor to American CyanamidCompany, New York, N.Y., a corporation of Maine No Drawing. ApplicationFebruary 28, 1958 7 Serial No. 718,131

8 Claims. Cl. 260-665) This invention relates broadly to a method ofproducing organometallic mixtures, and more particularly to a method ofpreparing a mixture of bis(lower alkyl-substitutedcyclopentadienyl)magnesium and bis(cyclopentadienyl)magnesium.

In my Patent No. 2,788,377, dated April 9, 1957, I have disclosed andclaimed the method of preparing dicyclopentadienylmagnesium[bis(cyclopentadienyl)magnesium] which comprises reacting, at atemperature of at least about 450 C., (l) a metal comprising magnesiumwith (2) at least one member of the class consisting .of cyclopentadieneand substances engendering cyclopentadiene.

The present invention is based on my discovery that, -when a procedureand reaction conditions somewhat similar to those disclosed in myaforementioned patent were :used in a reaction between (1) a loweralkyl-substitu-ted :cyclopentadiene, specifically methylcyclopentadiene,and {(2) a metal comprising magnesium, there was surprisingly obtained amixture of bis(methylcyclopentadienyDmag- :nesium andbis(cyclopentadienyl)magnesium instead ofbis(methylcyclopentadienyl)magnesium alone as normally would have beenexpected.

In practicing the present invention the reaction is effected at atemperature of at least about 450 C., and may range, for instance,between about 450 C. and :about 700 0., depending, for example, upon theparticular lower alkyl-substituted cyclopentadiene which is reacted withmagnesium (metallic magnesium) to produce 'the aforesaid organometallicmixture; flow rate of the organic reactant; and other influencingfactors. For instance, the reaction between magnesium and gaseousmethylcyclopentadiene is preferably effected at a temper- :ature ofbetween about 450 C. and about 600 C. The maximum temperature ofreaction in the case of the other lower alkyl-substitutedcyclopentadiene reactants [e.g., idimethylcyclopentadiene,trimethylcyclopentadiene, tetramethylcyclopentadiene, etc., and themonoand poly- (e.g., di-, tri-, tetra-, etc.) ethyl-, propyl-,isopropyl-, nbutyl-, isobutyl-, sec.-butyl-, tert.-butyl-, n-amyI-,isoamyl-, etc., cyclopentadienes] will normally be a little lower thanthe maximum temperature used when methylcyclopentadiene is the reactant.In general, the reaction is carried out at the lowest possibletemperature which is consistent with optimum yields and minimumdeposition of carbon in the reaction zone.

The reaction is preferably efiected while at least the loweralkyl-substituted cyclopentadiene is in gaseous state. However,liquid-phase reactions are not precluded, in which case superatmosphericpressure is used when necessary in order to keep the organic reactant inthe liquid state at the desired temperature. Also, metallic or othercatalysts may be employed to accelerate the reaction. If

desired, the reaction may be effected in the presence of an inert gas(that is, one which is inert both to the reactants and to the reactionproduct, e.g., nitrogen, helium, argon and krypton) thereby to provide,for example, better control of the reaction. Such a. gas also may serve2,933,537 Patented Apr. 19 1960 ICC 2 as a carrier for, or diluent of,the organic reactant. It also aids in removing the mixture of bis(loweralkylsubstituted cyclopentadienyl)magnesium andbis(cyclopentadienyl)magnesium from the reaction zone;

Instead of magnesium one can use an alloy of magnesium, e.g., amagnesium-aluminum alloy. Alloys of magnesium with a metallic catalystfo'r the reaction can be used. Instead of a single loweralkyl-substituted cycle pentadiene alone, one can'use mixtures thereofin any proportions.

It was quite surprising and unexpected that a mixture of a bis(loweralkyl-substituted cyclopentadienyl)rnagnesium andbis(cyclopentadienyl)magnesium could be produced by the method of thisinvention, especially since efforts to produce the correspondingbis(cyclopentadienyl) derivatives of other metals, specifically barium,aluminum, tin, zinc, uranium, cobalt, nickel and titanium by directreaction with cyclopentadiene at elevated temperatures were unsuccessful(reference: Patent No. 2,788,377, column 2, lines 1-5).

In order that those skilled in the art may better understand how thepresent invention can be carried into effect, the following examples aregiven by way of illustration and not by way of limitation. All parts andpercentages are by weight unless otherwise stated.

Example 1 methylcyclopentadiene in a reaction vessel provided with acolumn filled with glass heads; the cracking is continued at such a ratethat the temperature at the top of the column remains at about 73 C.,which is the boiling point of monomeric methylcyclopentadiene. From thetop of the column, the methylcyclopentadiene vapor is mixed with astream of an inert gas, specifically nitrogen, and the mixture is passeddirectly into the furnace. Suitable means are provided for controllingand measuring the temperature in the furnace.

At a temperature of about 500 C., a yellow liquid condensate deposits onthe walls of the tube outside the furnace. This liquid is subsequentlyidentified as a mixture of bis(methylcyclopentadienyl)magnesium andbis(cyclopentadienyl)magnesium dissolved in unreacted monomer. At highertemperatures (e.g., at about 600 C. and higher), the formation of themixture is more rapid but contamination of the product with organicmaterial is more likely to take place at such higher temperatures.

The reaction product is obtained as a yellow liquid which containsunreacted hydrocarbon and a mixture of substituted and unsubstitutedcyclopentadienyl magnesium compounds. This mixture reacts rapidly withwater to give both methylcyclopentadiene and cyclopentadiene (identifiedby mass spectroscopy). The mixture described above reacts rapidly withoxygen, but can be kept indefinitely if held under an inert atmosphere.This mixture (a liquid at room temperature) can be conveniently handledand transferred or may be dissolved in a suitable solvent for furtheruse.

Example 2 Same as Example 1 with the exception that the magnesium metalis in the form of magnesium turnings reacted monomer.

which are supported in a vertical furnace above a disc of Nichromegauze. The bed of ,turnings is heated by an electrical furnace to 525 C.The reaction temper ature may be conveniently measured. by means of athermocouple placed in a thermocpuplerwell,lqq ited at the center of teeommn rmagnesmm turning s."

' A stream o hi cy' op ad en t er; p qduccd .as is described in Example.1, is passed'.'dowri.through the heated ,columnof magnesium fturningsjThis yapor combines'with the hot magnesium to produce l a yell'cnvliquid mixturecontaininghis(icyclopentatlieriyl)rnagand bis(methylcyclopentadienyl)fnagnesium. This uid condenses o n' the eel r walls of thefurnacetube nd falls into a' receiver below the furnace. The product athen b use as r ssdru r fin an sen ate l l various app cat cn The todiswbtai ssi E se i l a solution in'u'nreacted: monomer of a rnixture of.cyclo- P a m s i iu sempo ndsc n a nin t (in thee?- ample describedhere) at'le' astj2'5 j% byw "g ht of methyl- Subsfitute-d b st ys entaeayllma nesium a d not w m than. 7.5% un ubs tute tsr l n ntadienyl)magnesium.

The composition of the mixture of this example (and of others producedby the methodof-this inyention) dependson the conditions under whichthe. process is carried v out; higher temperatures and longer residencetime produce more unsubstituted compound and less pnreacted Same as inExample 1 with the exception that the organic reactant "isethylcyclopentadiene monomer, and the maximum temperature of reaction isabout 600 C., the major portion of the-reaction beingcaused to takeplace within the temperature range of from about 475 C. to about 550 C..The product, which is collected as in Example 1, comprises a mixtureof-bis(-ethylcyc1 opentadienyDmagnesium and bi s(cyclopentadienyl)magnesium.

' Example4 Same s in Example 1 w t t e exc fiq ha e organic reactant ispropylcyclopentadiene monomer, and the maximum temperature of reactionis about 600 C., the major portion of thereaction being caused to takeplace withinthe temperature range of from about 475 C. to about 550C.The product, which is collected as in Example 1, comprises a mixture ofhis (propylcyclopentadienyllmagnesium and bis(cyclopendadienyl-)magnesium.

Instead of methyl-, ethylor propylcyclopentadiene monomer specificallyemployed in the foregoing examples, one can use any other monoorpoly-(lower alkyl-substituted) cyclopentadiene, or mixtures thereof inany. proportions, numerous examples of which have been given in theportion of this specification prior to the examples.

Example 5 t y e g from wh ch?. el m i it .b rna eh high-pressurepolymerization technique, and which contains an objectionably highamount of oxygen when the gas is to be used for this purpose, is bubbledthrough a 5% solution of about equal parts by weight ofhismethylcyclopentadienyl) magnesium and bis (cyclopentadienyDmagnesiumin purified'tetrahydrofuran at 10 C., using 'a'closed system. Afterpassagejthrough the aforesaid solution, the oxygen content of..theethylene is sufliciently reduced so that the ethylene can be 1successfully polymerized under high pressure.

In addition to their use as" an oxygen scavenger, mine tures ofbis(loweralkyl-substituted cyclopentadienyDmagnesium andbis(cyclopentadienyl)magnesium are also useful as an intermediate inchemical reactions, e.g., as a reactant with carbon dioxide to yieldsalts of a mixture of dicyclopentadiene dicarboxylic acids; as areactant with metallic salts (e. g., metallichalides such, for instance,as Fe'Cl NiCl MnCl etc.) to yield a mixture of unsubstituted and loweralkyl-substituted cyclopentadienyl metal compounds that can be separatedfrom each other by conventional methods; as'hypergolic agents; etc.

It is possible that, in addition to bis(lower alkyl-substituted"cyclopentadienyl)magnesium and bis(cyclopentadienyDmagnesium, themixtures of the present invention also contain so-called mixedcompounds, that is, cyclopentadienylmagnesium compounds wherein a' loweralkyl group, e,g., the methyl group, is substituted on only one ring.However, the presence of sucha compound in the mi tu ei ifli tarsflbfishco c us v yl. The method of preparing a mixture of a bis-(loweralkyl-substituted cyclopentadienyl)magnesium and his-(cyclopentadienyl)magnesium'which comprises reacting, at a temperatureof at least' about 450 C., (1) a metal comprising magnesium with (2) alower alkyl-substituted cyclopentadiene; and collecting theproductcomprising the aforesaid mixture.

2. A method as in claiml wherein thereactant of (2) is -in a gaseousstate. i

'3. A method as in claim'l wherein the reaction is efiected in thepresence of an inert gas.

. 4. flhe method of preparing a mixture of bis(rnethylcyclopentadienyl)magnesium and bis(cyclopentadienyl) magnesium which comprises reacting,.at a temperature ofat least about 450 C, (l) a metal comprising-magnesum w t .(2) mq l lopr adi ne;and r fl c e .pr du s r pris n thea r aid mxtur 5 msthes a inla 4 whe e n th r a t n 9 isine ese i state- 6. Amethod as in claim 4 wherein the reaction is etfected inthe presence ofan inert gas.

7. 'The method of preparinga mixture of bis(n1et hyls lo ad e )ma n iuma i t lq tadi ynmagnesium which comprises reacting together magnesiumand gaseous methylcyclopentadiene, said reaction being effected at atemperature of between about 450 C. and about 600 C.; and collecting theproduct comprising the aforesaid mixture. V

' 8. A method as in claim 7 wherein the reaction is effected in thepresentment an inert gas.

Barber 7 Apr. '9, 1957 .Br v reys-1.2195

1. THE METHOD OF PREPARING A MIXTURE OF A BIS-(LOWER ALKYL-SUBSTITUTEDCYCLOPENTADIENYL)MAGNESIUM AND BIS(CYCLOPENTADIENYL)MAGNESIUM WHICHCOMPRISES REACTING, AT A TEMPERATURE OF AT LEAST ABOUT 450* C., (1) AMETAL COMPRISING MAGNESIUM WITH (2) A LOWER ALKYL-SUBSTITUTEDCYCLOPENTADIENE, AND COLLECTING THE PRODUCT COMPRISING THE AFORESAIDMIXTURE.